Factor V Leiden thrombophilia

Factor V is part of the blood-clotting cascade. The Leiden variant makes clotting harder to switch off, raising the risk of vein clots, especially around surgery, immobility, pregnancy or estrogen use.

Possible results

No clotting variant. You don't carry Factor V Leiden, the most common inherited clotting variant. From what this gene shows your blood's clotting off-switch works normally and your clot risk is at baseline.

Higher clot risk. You carry one copy of Factor V Leiden, a variant that makes it harder for your body to switch off clotting. This raises your risk of clots in the veins, especially during long immobility, surgery, pregnancy, or while using estrogen-containing birth control. Most carriers never have a clot, but it's useful to know in those situations.

High clot risk. You have two copies of Factor V Leiden, which more strongly raises the risk of vein clots because your clotting is harder to switch off. This is worth discussing with a doctor, particularly around surgery, pregnancy, long travel, or hormone use, where extra precautions can lower the risk.

Evidence & sources

Across global populations, fewer than 1% of people carry two copies of this variant, and about 96% carry none.

This variant appears in 13 published genetic studies: PubMed 22672568 · PubMed 25772935 · PubMed 26908601 · PubMed 28373160 · PubMed 31420334 · PubMed 31676865 · PubMed 33592630 · PubMed 35285134 · PubMed 36154123 · PubMed 36777996 · PubMed 38561338 · PubMed 39789286 · PubMed 41298473.

Related

Atrial fibrillation risk (4q25) · Crohn's disease susceptibility · HbA1c (blood sugar) · Prothrombin clotting variant · Rheumatoid arthritis · Uric acid / gout tendency · Venous thromboembolism (clots)